494 PATHOGENIC MICROORGANISMS 



purposes by instillation into the conjunctival sac. In tuberculous 

 patients this process is followed by a sharp conjunctival congestion 

 lasting from one to several days. 



The preparation used for this purpose is produced in the following 

 way: 



"Old Tuberculin" is treated with double the quantity of 95 per 

 cent alcohol, and the precipitate allowed to settle and the alcohol then 

 filtered off through paper. The sediment is washed with 70 per cent 

 alcohol until the filtrate runs clear, then pressed between layers of 

 filter paper to remove excess of moisture, scraped into a dish, dried 

 in vacua over H 2 S0 4 , and broken up in a mortar under a hood. 



Solutions of the powder are made in sterile normal salt solution, 1 

 per cent by weight, boiled and filtered. The solutions are used in 

 strengths of 0.5 to 1 per cent, a drop of which is instilled j into the con- 

 junctival sac. 1 



Cutaneous Tuberculin Reaction. Von Pirquet 2 has suggested the 

 cutaneous use of tuberculin for diagnostic purposes. A 25 per cent 

 solution of "Old Tuberculin" was first used. At present the undi- 

 luted substance is employed. 



After sterilization of the patient's forearm, two drops of this solu- 

 tion are placed upon the skin about 6 cm. apart. Within each of these 

 drops scarification is done, and the skin between them sacrificed as a 

 control. Within twenty-four to forty-eight hours, in tuberculous 

 patients, erythema, small papules, and herpetiform vesicles will ap- 

 pear. According to recent investigations, about 70 per cent of adults 

 show a positive reaction. This reverses its diagnostic value for adults. 



Moro 3 has modified this by simply making a 50 per cent ointment 

 of tuberculin in lanolin and rubbing it into the skin without scari- 

 fication. 



Complement Fixation in Tuberculosis.* The problem of comple- 

 ment fixation in tuberculosis for diagnostic purposes has been very 

 actively investigated of recent years. The most promising results have 

 been reported with an antigen made by Besredka of a filtrate of an 

 egg-meat-broth, upon which culture the tubercle bacilli had been grown 

 for several weeks ; a similar filtrate of cultures on a watery extract of 



1 Method in use at Saranac and kindly communicated by Dr. Baldwin. 



2 v. Pirquet, Berl. klin. Woch., xx, 1907; Med. Klinik, xl, 1907. 

 Moro, Munch, med. Woch., 1906, p. 216. 



4 A review of complement fixation tests in tuberculosis will be found in an article 

 by H. R. Miller, Jour. I ab. & Clin. Med., 1916, i, 816. 



